Influence of pore size on the piezoresistive behavior of CNT/PDMS sponge sensors

Abstract

Flexible thermoplastic polyurethane (TPU) nanocomposites reinforced with multi-walled carbon nanotubes (MWCNTs) and manufactured using a scalable two-step process involving extrusion and hot pressing are proposed. This work systematically investigates the role of CNT dispersion and shear forces during the extrusion process in optimizing the electrical conductivity of TPU/CNT nanocomposites via analytical modeling. More specifically, the combination of percolation threshold, scaling law and shear force models is proposed in this study to identify the role of the most critical parameters in electrical properties. A 3-minute dispersion time emerges as the optimal condition, yielding conductivities of 0.071 ± 0.055 S/m for 6 wt.% CNT filaments while minimizing nanoparticle breakage. The model revealed that longer dispersion times, higher torques or higher shear forces in the TPU-CNT mixture, would lead to a more prevalent breakage of the nanoparticles, resulting in a reduction of their aspect ratio and the aggregation parameters. Hot pressing further enhanced conductivity to a maximum of 9.60 ± 1.36 S/m by homogenizing CNT distribution and minimizing agglomeration. The combined experimental and theoretical approaches establish a robust framework for designing